Cardiac arrhythmias can be treated pharmacologically, surgically, or by the implantation of a medical device. In the case of a tachycardia it is now common to perform endocardial mapping to determine the origin and mechanism of the arrythmia prior to selecting a therapeutic approach. Endocardial mapping can also be used to monitor or assess the efficacy of a therapy once selected and delivered.
Traditionally endocardial mapping techniques involve the introduction of one or more catheters into the patient, advancing the catheters through a blood vessel and placing the catheters in a heart chamber. Once located in the heart, the electrode or electrodes of the catheters are pressed against the endocardial surface to record the electrical potential of the cardiac tissue at that electrode site. Single electrode contact systems are tedious to use but they do not interfere with the normal blood flow through the heart. Multiple electrode contact systems are also available to permit simultaneous mapping of potentials from several electrode sites. However some of these systems block blood flow through the heart. Multiple electrode systems which do not interfere with the blood flow, and which do not contact the surface of the heart are also known, although these systems do not permit a high resolution map of the endocardial surface.
U.S. Pat. No. 4,649,924 to Taccardi teaches a catheter which is inserted into the heart chamber. The distal end of this catheter is formed into an elliptical shape which is much smaller than the heart chamber. The multiple electrodes on the surface of this ellipsoid may be used to detect the electrical potential produced by the area of the endocardial surface proximate each individual electrode. Accurate measurements require that the electrodes do not touch the endocardial surface. This type of catheter floats freely in the heart chamber but will typically touch the walls of the beating heart. The constant motion of the catheter and contact with the walls frustrates accurate measurement of the cardiac potentials. Therefore these prior non-contact mapping and in-contact mapping catheters compromise the accuracy of the resultant map with the ease of use. Therefore there is a need for a catheter which can be used to develop an accurate representation of the electrical activity of the heart.